Hi,
so, I'm currently facing this issue, where I would like to do some calls to
an external service, when my object has been deleted within a flush.
For this operation to occur, I need the id from my model object, but also
the id from the parent of the parent object model. There are cases, where I
am unable to access them (I guess, depending of the order of the execution)
and I am unsure on what to do next.
So if you're willing to give me some advice, would be awesome.
Here is a dummy model:
from sqlalchemy import event
from sqlalchemy import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, backref, relationship
Base = declarative_base()
#########################################################################################
# MODEL
#########################################################################################
class House(Base):
__tablename__ = 'house'
id = Column(Integer, primary_key=True)
rooms = relationship("Room",
backref=backref("house", lazy="joined"),
cascade='all, delete-orphan')
class Room(Base):
__tablename__ = 'room'
id = Column(Integer, primary_key=True)
house_id = Column(Integer, ForeignKey('house.id'))
beds = relationship("Bed",
backref=backref("room", lazy="joined"),
cascade='all, delete-orphan')
class Bed(Base):
__tablename__ = 'bed'
id = Column(Integer, primary_key=True)
room_id = Column(Integer, ForeignKey('room.id'))
#########################################################################################
# CONFIG
#########################################################################################
def setup():
engine = create_engine("sqlite:///foo.db", echo=True)
Base.metadata.bind = engine
Base.metadata.create_all(engine)
SessionFactory = sessionmaker(
bind=engine
)
event.listen(SessionFactory, 'deleted_to_detached',
listener_bed_has_been_removed)
return SessionFactory
def listener_bed_has_been_removed(session, instance):
if type(instance) is not Bed:
return
bed_id = instance.id
house_id = instance.room.house.id # this is NOT ALWAYS there. Depending on
the order of the execution I guess
print("execute the service call to external service here bed_id {},
house_id {}".format(bed_id, house_id))
So my question(s):
- Is there a clean way to always acces this parent's parent attribute?
- If not, would be starting a new session and query it from the event
handler be an option? (is it not dangerous, because it seems to work)
- Additional quirk, I am working within a transaction manager
(pyramid_tm) and ZopeTransactionExtension()
Thanks!
More information about the system:
SQLAlchemy 1.1.13
Python 3.5
Postgres 9.6
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
---
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to sqlalchemy+unsubscr...@googlegroups.com.
To post to this group, send email to sqlalchemy@googlegroups.com.
Visit this group at https://groups.google.com/group/sqlalchemy.
For more options, visit https://groups.google.com/d/optout.
